Engine Cranks But Does Not Run
Engine Cranks But Does Not Run
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
Circuit/System Description
This Engine Cranks but Does Not Run diagnostic is an organized approach to identify a condition which causes the engine to crank but does not continue to run. This diagnostic directs the service technician to the appropriate system diagnosis. This diagnostic assumes the vehicle system voltage levels are adequate for starter motor operation. Refer to Battery Inspection/Test (Battery Inspection/Test) and Engine Cranks Slowly (Engine Cranks Slowly). The fuel level supply must be adequate, and the fuel quality must be able to sustain the combustion process.
Diagnostic Aids
* When disconnecting electrical connectors or removing fuses and relays from a fuse block, always inspect both mating electrical terminals for corrosion and terminal tightness.
* Use the J 35616 GM-Approved Terminal Test Kit for any test that requires probing the underhood fuse block terminals, component wire harness terminals, or the ECM wire harness terminals.
Reference Information
Schematic Reference
Engine Controls Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Special Tools
* J 34730-1A Fuel Pressure Gage
* J 35616 GM-Approved Terminal Test Kit
* J 35616-A/BT-8637 Connector Test Adapter Kit
* J 43244 Relay Puller Pliers
Circuit/System Verification
Attempt to start the engine. The engine should start and run.
If the vehicle passes the Circuit/System Verification test, refer to Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics).
Circuit/System Testing
1. Crank the engine for up to 30 seconds.
2. Observe the vehicle DTC information with a scan tool.
• If any of the following DTCs are set, diagnose these DTCs first: DTC P0117, P0118, P0122, P0123, P0201-P0208, P0222, P0223, P0335, P0336, P0351-P0358, P0562, P0563, P0601-P0604, P0606, P0607, P062F, P0633, P0685, P0690, P1631, P1682, or P2610. Refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code Descriptions).
3. With the ignition ON and the engine OFF, test the fuses that are supplied ignition 1 voltage by the powertrain relay. The test lamp should illuminate ON for each test point of the fuses.
• If the test lamp does not illuminate ON for at least one test point of each fuse, refer to DTC P0685, P0689, or P0690 (P0685).
4. Crank the engine for 15 seconds. Observe the engine speed parameter with a scan tool.
• If engine RPM is not indicated, refer to DTC P0335 (P0335).
5. Install a spark plug tester onto one ignition module/coil assembly on each bank of the engine.
6. Observe both spark plug testers.
Note: An erratic or weak spark is considered a no spark condition.
7. Crank the engine for 15 seconds. The ignition coil secondary voltage should be observed across the gap of both spark plug testers.
• If the ignition coil secondary voltage is not observed, is inconsistent, or weak on either spark plug tester, refer to Electronic Ignition System Diagnosis (Electronic Ignition System Diagnosis).
8. With the ignition ON and the engine OFF, command the fuel pump ON and OFF with the scan tool. The fuel pump should energize when commanded ON, and de-energize when commanded OFF.
• If the fuel pump does not turn ON and OFF, refer to Fuel System Diagnosis (Fuel System Diagnosis).
9. Turn OFF the ignition.
10. Install the J 34730-1A Fuel Pressure Gage. With the ignition ON and the engine OFF, command the fuel pump ON several times with the scan tool. Refer to Fuel System Diagnosis (Fuel System Diagnosis) for the fuel pressure specification.
11. Inspect for the following conditions:
* Compare the actual engine coolant temperature to the ECT parameter.
* Filter and air intake system for restrictions and obstructions
* Test the fuel for contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Alcohol/Contaminants-in-Fuel Diagnosis).
* Inspect the spark plugs-Refer to Spark Plug Inspection (Testing and Inspection).
* Test the exhaust system for restrictions-Refer to Restricted Exhaust (Restricted Exhaust).
* Engine mechanical conditions, such as worn timing chain, sprocket gears, low compression, etc.-Refer to Symptoms - Engine Mechanical (- Symptoms - Engine Mechanical).
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.